diff options
Diffstat (limited to 'Documentation/arm/nwfpe')
| -rw-r--r-- | Documentation/arm/nwfpe/index.rst | 13 | ||||
| -rw-r--r-- | Documentation/arm/nwfpe/netwinder-fpe.rst (renamed from Documentation/arm/nwfpe/README.FPE) | 24 | ||||
| -rw-r--r-- | Documentation/arm/nwfpe/notes.rst (renamed from Documentation/arm/nwfpe/NOTES) | 3 | ||||
| -rw-r--r-- | Documentation/arm/nwfpe/nwfpe.rst (renamed from Documentation/arm/nwfpe/README) | 10 | ||||
| -rw-r--r-- | Documentation/arm/nwfpe/todo.rst (renamed from Documentation/arm/nwfpe/TODO) | 47 |
5 files changed, 64 insertions, 33 deletions
diff --git a/Documentation/arm/nwfpe/index.rst b/Documentation/arm/nwfpe/index.rst new file mode 100644 index 000000000000..3c4d2f9aa10e --- /dev/null +++ b/Documentation/arm/nwfpe/index.rst @@ -0,0 +1,13 @@ +.. SPDX-License-Identifier: GPL-2.0 + +=================================== +NetWinder's floating point emulator +=================================== + +.. toctree:: + :maxdepth: 1 + + nwfpe + netwinder-fpe + notes + todo diff --git a/Documentation/arm/nwfpe/README.FPE b/Documentation/arm/nwfpe/netwinder-fpe.rst index 26f5d7bb9a41..cbb320960fc4 100644 --- a/Documentation/arm/nwfpe/README.FPE +++ b/Documentation/arm/nwfpe/netwinder-fpe.rst @@ -1,12 +1,18 @@ +============= +Current State +============= + The following describes the current state of the NetWinder's floating point emulator. In the following nomenclature is used to describe the floating point instructions. It follows the conventions in the ARM manual. -<S|D|E> = <single|double|extended>, no default -{P|M|Z} = {round to +infinity,round to -infinity,round to zero}, - default = round to nearest +:: + + <S|D|E> = <single|double|extended>, no default + {P|M|Z} = {round to +infinity,round to -infinity,round to zero}, + default = round to nearest Note: items enclosed in {} are optional. @@ -32,10 +38,10 @@ Form 2 syntax: <LFM|SFM>{cond}<FD,EA> Fd, <count>, [Rn]{!} These instructions are fully implemented. They store/load three words -for each floating point register into the memory location given in the +for each floating point register into the memory location given in the instruction. The format in memory is unlikely to be compatible with other implementations, in particular the actual hardware. Specific -mention of this is made in the ARM manuals. +mention of this is made in the ARM manuals. Floating Point Coprocessor Register Transfer Instructions (CPRT) ---------------------------------------------------------------- @@ -123,7 +129,7 @@ RPW{cond}<S|D|E>{P,M,Z} Fd, Fn, <Fm,#value> - reverse power POL{cond}<S|D|E>{P,M,Z} Fd, Fn, <Fm,#value> - polar angle (arctan2) LOG{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - logarithm to base 10 -LGN{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - logarithm to base e +LGN{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - logarithm to base e EXP{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - exponent SIN{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - sine COS{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - cosine @@ -134,7 +140,7 @@ ATN{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - arctangent These are not implemented. They are not currently issued by the compiler, and are handled by routines in libc. These are not implemented by the FPA11 -hardware, but are handled by the floating point support code. They should +hardware, but are handled by the floating point support code. They should be implemented in future versions. Signalling: @@ -147,10 +153,10 @@ current_set[0] correctly. The kernel provided with this distribution (vmlinux-nwfpe-0.93) contains a fix for this problem and also incorporates the current version of the emulator directly. It is possible to run with no floating point module -loaded with this kernel. It is provided as a demonstration of the +loaded with this kernel. It is provided as a demonstration of the technology and for those who want to do floating point work that depends on signals. It is not strictly necessary to use the module. -A module (either the one provided by Russell King, or the one in this +A module (either the one provided by Russell King, or the one in this distribution) can be loaded to replace the functionality of the emulator built into the kernel. diff --git a/Documentation/arm/nwfpe/NOTES b/Documentation/arm/nwfpe/notes.rst index 40577b5a49d3..102e55af8439 100644 --- a/Documentation/arm/nwfpe/NOTES +++ b/Documentation/arm/nwfpe/notes.rst @@ -1,3 +1,6 @@ +Notes +===== + There seems to be a problem with exp(double) and our emulator. I haven't been able to track it down yet. This does not occur with the emulator supplied by Russell King. diff --git a/Documentation/arm/nwfpe/README b/Documentation/arm/nwfpe/nwfpe.rst index 771871de0c8b..35cd90dacbff 100644 --- a/Documentation/arm/nwfpe/README +++ b/Documentation/arm/nwfpe/nwfpe.rst @@ -1,4 +1,7 @@ -This directory contains the version 0.92 test release of the NetWinder +Introduction +============ + +This directory contains the version 0.92 test release of the NetWinder Floating Point Emulator. The majority of the code was written by me, Scott Bambrough It is @@ -31,7 +34,7 @@ SoftFloat to the ARM was done by Phil Blundell, based on an earlier port of SoftFloat version 1 by Neil Carson for NetBSD/arm32. The file README.FPE contains a description of what has been implemented -so far in the emulator. The file TODO contains a information on what +so far in the emulator. The file TODO contains a information on what remains to be done, and other ideas for the emulator. Bug reports, comments, suggestions should be directed to me at @@ -48,10 +51,11 @@ Legal Notices The NetWinder Floating Point Emulator is free software. Everything Rebel.com has written is provided under the GNU GPL. See the file COPYING for copying -conditions. Excluded from the above is the SoftFloat code. John Hauser's +conditions. Excluded from the above is the SoftFloat code. John Hauser's legal notice for SoftFloat is included below. ------------------------------------------------------------------------------- + SoftFloat Legal Notice SoftFloat was written by John R. Hauser. This work was made possible in diff --git a/Documentation/arm/nwfpe/TODO b/Documentation/arm/nwfpe/todo.rst index 8027061b60eb..393f11b14540 100644 --- a/Documentation/arm/nwfpe/TODO +++ b/Documentation/arm/nwfpe/todo.rst @@ -1,39 +1,42 @@ TODO LIST ---------- +========= -POW{cond}<S|D|E>{P,M,Z} Fd, Fn, <Fm,#value> - power -RPW{cond}<S|D|E>{P,M,Z} Fd, Fn, <Fm,#value> - reverse power -POL{cond}<S|D|E>{P,M,Z} Fd, Fn, <Fm,#value> - polar angle (arctan2) +:: -LOG{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - logarithm to base 10 -LGN{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - logarithm to base e -EXP{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - exponent -SIN{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - sine -COS{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - cosine -TAN{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - tangent -ASN{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - arcsine -ACS{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - arccosine -ATN{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - arctangent + POW{cond}<S|D|E>{P,M,Z} Fd, Fn, <Fm,#value> - power + RPW{cond}<S|D|E>{P,M,Z} Fd, Fn, <Fm,#value> - reverse power + POL{cond}<S|D|E>{P,M,Z} Fd, Fn, <Fm,#value> - polar angle (arctan2) + + LOG{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - logarithm to base 10 + LGN{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - logarithm to base e + EXP{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - exponent + SIN{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - sine + COS{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - cosine + TAN{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - tangent + ASN{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - arcsine + ACS{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - arccosine + ATN{cond}<S|D|E>{P,M,Z} Fd, <Fm,#value> - arctangent These are not implemented. They are not currently issued by the compiler, and are handled by routines in libc. These are not implemented by the FPA11 -hardware, but are handled by the floating point support code. They should +hardware, but are handled by the floating point support code. They should be implemented in future versions. There are a couple of ways to approach the implementation of these. One -method would be to use accurate table methods for these routines. I have +method would be to use accurate table methods for these routines. I have a couple of papers by S. Gal from IBM's research labs in Haifa, Israel that seem to promise extreme accuracy (in the order of 99.8%) and reasonable speed. These methods are used in GLIBC for some of the transcendental functions. Another approach, which I know little about is CORDIC. This stands for -Coordinate Rotation Digital Computer, and is a method of computing +Coordinate Rotation Digital Computer, and is a method of computing transcendental functions using mostly shifts and adds and a few multiplications and divisions. The ARM excels at shifts and adds, -so such a method could be promising, but requires more research to +so such a method could be promising, but requires more research to determine if it is feasible. Rounding Methods +---------------- The IEEE standard defines 4 rounding modes. Round to nearest is the default, but rounding to + or - infinity or round to zero are also allowed. @@ -42,8 +45,8 @@ in a control register. Not so with the ARM FPA11 architecture. To change the rounding mode one must specify it with each instruction. This has made porting some benchmarks difficult. It is possible to -introduce such a capability into the emulator. The FPCR contains -bits describing the rounding mode. The emulator could be altered to +introduce such a capability into the emulator. The FPCR contains +bits describing the rounding mode. The emulator could be altered to examine a flag, which if set forced it to ignore the rounding mode in the instruction, and use the mode specified in the bits in the FPCR. @@ -52,7 +55,8 @@ in the FPCR. This requires a kernel call in ArmLinux, as WFC/RFC are supervisor only instructions. If anyone has any ideas or comments I would like to hear them. -[NOTE: pulled out from some docs on ARM floating point, specifically +NOTE: + pulled out from some docs on ARM floating point, specifically for the Acorn FPE, but not limited to it: The floating point control register (FPCR) may only be present in some @@ -64,4 +68,5 @@ would like to hear them. Hence, the answer is yes, you could do this, but then you will run a high risk of becoming isolated if and when hardware FP emulation comes out - -- Russell]. + + -- Russell. |